Preparation of stereoregular polyvinyl alcohol shaped articles

ABSTRACT

1,102,771. Producing stereoregular polyvinyl alcohol fibres. MONSANTO CO. 8 April, 1965 [8 April, 1964], No. 14981/65. Heading B5B. Stereoregular polyvinyl alcohol filaments which are insoluble in boiling water are produced by wet or dry spinning a solution of a stereoregular polyvinyl ester of a halogenated acetic acid, in which all three hydrogen atoms of the methyl group in the acetic acid have been substituted by either chlorine or fluorine or by both fluorine and chlorine, and continuously hydrolysing the resulting filaments. The filaments are preferably formed by wet spinning, and the thus formed filaments, stretched, hydrolysed continuously, dried and hot drawn. The spinning solution may contain 12 to 40% by weight of the polyester dissolved in an organic oxygen-containing liquid and may be extruded into a coagulation liquid which is a non-solvent for the polymer but miscible with the spinning solution solvent. The filaments may be stretched immediately after hydrolysis. The organic oxygen containing liquid may be acetone, methyl ethyl ketone, tetrahydrofuran or dimethylacetamide. The coagulating bath may be aqueous. The filaments may be hydrolysed with a base having a pKb value less than 8À0, such as ammonium hydroxide, methanolic ammonia, tetramethyl ammonium hydroxide or a primary or secondary amine. The freshly extruded polyester filaments may be stretched at a draw ratio of 1À05 to 8À0 : 1À0 in a hot aqueous bath, and may be further stretched immediately after hydrolysis. They may then be dried by passing them over a roller maintained at a temperature of from 80‹ to 110‹ C. and finally drawn over a heated surface while stretching them at a stretch ratio of from 1À1 to 5À0 : 1À0. The ester spun may be vinyltrifluoro or chlorodofluoroacetate.

July 4. 1967 w. 5. BLACK PREPARATION OF STEREOREGULAR POLYVINYL ALCOHOL SHAPED ARTICLES Filed April 8, 1964 Had mjom mo V 12m W5 For I NVEN TOR. WILLIAM B. BLACK ATTORNEY United States Patent 3,329,754 PREPARATION OF STEREOREGULAR POLY- VINYL ALCOHUL SHAPED ARTICLES William B. Black, Raleigh, N.C., assignor to Monsanto Company, St. Louis, Mo., a corporation of Delaware Filed Apr. 8, 1964, Ser. No. 358,243 16 Claims. (Cl. 264184) This invention relates to the production of shaped articles of stereo-regular polyvinyl alcohol by a solution spining method. More particularly, this invention is concerned with the production of fibers, filaments, and films from such polymers of stereo-regular polyvinyl alcohol by the spinning of solutions of polyvinyl esters of halogenated acetic acids and the subsequent continuous conversion of the resulting shaped article by hydrolysis to stereo-regular polyvinyl alcohol shaped articles.

Polyvinyl alcohol has'long been recognized as an attractive polymer well suited for the production of fibers and filaments. However, its wide utilization for this purpose has been hindered by its solubility in water. Various approaches have been used to circumvent this deficiency in polyvinyl alcohol. Initially, polyvinyl alcohol articles when unmodified are quite soluble in water and particularly in hot water so that they are totally unsuitable for use as textile fibers for the production of fabrics and garments which can be laundered or otherwise exposed to water. Subsequently, it was discovered that such polyvinyl alcohol shaped articles could be treated with agents such as aldehydes, particularly formaldehyde, which treatment results in an insoluble fiber in cold and hot water by partially cross-linking the polymer. However, the formaldehyde treatment resulted in a loss of many desirable characteristics of the initial polymer articles, They were rendered quite rough and stiff and the degree of cross-linking by the various agents had to be strictly controlled in order to produce fibers which were suitable for use in textile products. Furthermore, the addition of this crosslinking or post treating step involves additional factors of cost which rendered the articles producted from the polyvinyl alcohol polymers less attractive for commercial purposes. In addition to aldehyde treatment several other mutually related approaches to making polyvinyl alcohol fibers less sensitive to water have been investigated and reported. In general, common to these processes 'is the use of a highly hydrolized water soluble polyvinyl alcohol for spinning, the use of a separate hot draw step, and absence of a chemical after treatment. In each case fiber which is insoluble in boiling water is reported. In several of these processes polyvinyl alcohol derived from conventionally prepared polyvinyl acetate is employed. The other processes use polyvinyl alcohols derived from a polyvinyl acetate or a polyvinyl formate which has been prepared under special conditions. In all of these processes, however, the polyvinyl alcohol which is spun is more soluble than the fiber obtained. Although some of the polymers used in these processes are undoubtedly marginally different in structure from conventional polyvinyl alcohols, the success of the process in every case is apparently the result of a hot drawing step. Excellent ordering of the molecules in the fiber appears to be the real key to the insolubility of the fibers produced. All fibers reported from such processes have elongations too low for many textile uses, with percent elongation being a typical upper limit. This low elongation appears to be an inherent property of water insoluble fibers prepared from water soluble polymer.

Recently there has been reported the preparation of highly stereo-regular polyvinyl alcohol. This highly stereoregular polymeric material, in contrast to the normal polyvinyl alcohol, is completely insoluble in both cold and hot 3,329,754 Patented July 4, 1967 water, including boiling water. The insolubility of stereoregular polyvinyl alcohol in water at C. has been attributed to the stereo-regularity of the alcohol as contrasted to the non-stereoregular structure possessed by conventional polyvinyl alcohol. Unfortunately, however, the polymer is likewise insoluble in practically all known solvents. For this reason, no practical wet or dry spinning process has to date been developed at least on a commercial basis which employs the recently prepared highly stereoregular polyvinyl alcohol polymers. Furthermore, the stereoregular polyvinyl alcohol polymers do not melt without drastic decomposition, and therefore no process for melt extruding shaped articles from these polymers appears to be practical. Therefore, although an excellent material for the fabrication of shaped articles, including films, fibers, filaments and so forth has now been developed, there still remains no practical commercial man ner of forming such articles from these polymers.

The use of the term stereoregular herein refers to a particular characteristic of certain polymers which has become a well known phenomenon. Both the polyvinyl trihaloacetates and the derived polyvinyl alcohols are believed to have the syndiota-tic type of stereoregularity.

It is an object of the present invention to provide a method for preparing shaped articles and particularly filaments and fibers of highly stereoregular polyvinyl alcohol.

A further object of the invention is to prepare strong high tenacity filaments and fibers of stereoregular polyvinyl alcohol exhibiting excellent textile properties.

Another object is the preparation of filaments and fibers of highly stereoregular polyvinyl alcohol which do not require cross-linking or other post treatments for the development of good wet and dry strength.

A still further object is the production of boiling water insoluble high elongation filaments and fibers of stereoregular polyvinyl alcohol which are well suited for the production of textile materials for apparel and other textile uses.

An additional object is the preparation of very high tenacity fibers of stereoregular polyvinyl alcohol.

Another object is the provision of fibers of low elongation suitable for use as reinforcing fibers in plastics.

Yet another object of the invention is the provision of a wet spinning method for the preparation of filaments and fibers of stereoregular polyvinyl alcohol which is capable of successful commercial continuous spinning thereby producing suitable and salable filaments and fibers for a wide range of uses.

Other objects of this invention will become apparent from the description thereof hereinafter.

These and other objects of the present invention are preferably accomplished by a process of wet spinning solutions of stereoregular polyvinyl esters of halogenated acetic acids into a coagulating medium therefor, subsequently hydrolizing the polyvinyl halogenated aliphatic acid ester in the form of a shaped article substantially to stereoregular polyvinyl alcohol by means of a base having a pKb value less than 8.0, and thereafter drying and heat stretching the resulting stereoregular polyvinyl alcohol article. Alternatively a dry spinning method may be used.

The shaped articles which are hydrolyzed are prepared from polymers of vinyl esters of halogenated lower aliphatic acids selected from monomeric compounds having the formula wherein X is a halogen selected from the group consisting of chlorine, fluorine and mixtures thereof. The vinyl esters 3 of halogenated acetic acids which are suitable for the present invention include vinyl trifiuoroacetate, vinyl monochlorodifiuoroacetate, vinyl dichl-oromonofluoroacetate, vinyl trichloroacetate and the like.

The highly stereoregular polymers of the vinyl esters of the halogenated acetic acids identified above can be produced by methods known in the art. Thus they may be produce by a free radical polymerization process at low temperatures employing free radical catalysts such as tr-in butyl boron with or Without other organic diluents such as heptane, cyclohexane, and so forth. Polymers with a lower degree of stereoregularity can be produced at temperatures above C. by means of these catalysts. However, in order to obtain highly stereoregul-ar polymers these polymerizations should be conducted at temperatures of from 0 C. to as low as about 95 C. to -100 C. The degree of stereoregularity of the resulting polymers increases with lowering temperature. Preparation at -50 C. to 78 C. is preferred with no substantial differences in properties of polymer prepared in this range and those of polymer prepared at lower temperatures.

The spinning of the stereoregular polyvinyl esters of haloacetic acids may be accomplished by any of the well known wet or dry spinning methods. Any convenient solvent that will dissolve stereoregular polyvinyl esters of haloacetic acids is suitable for use in the spinning process. Useful solvents include organic liquids which contain oxygen in the form of ether or carbonyl. These solvents include acetone, methyl ethyl ketone, ethyl acetate, dimethylformamide, dimethylacetamide, cyclohexanone, tetrahydrofuran, methyl formate and the like.

In a preferred wet spinning process the coagulating bath can be any liquid which is a solvent or is misable with the solvent employed in the spinning solution but is a non-solvent for the polymer. Both polar and non-polar liquids may be employed but polar 'ones are preferred such as water.

Immediately after coagulation the fiber is subjected to a hot stretch prior to hydrolysis. This heat stretch operation involves a simultaneous wash stretch in the hot water bath. The fiber is subjected to a stretch of from about 1.05 to 8.0 times while passing through the hot water bath.

At this point in the continuous process of the invention the fiber is now ready for the hydrolysis step whereby the fiber is converted to a polyvinyl alcohol fiber. As used herein the term hydrolysis includes any reaction whereby the polyvinyl ester of halogenated acetic acids are converted to polyvinyl alcohol. The hydrolysis is conveniently conducted by winding the fiber on a series of one or more godets which wet and hydrolyze the fibers while passing around the godets. The hydrolysis agent can be any base with a pKb value less than 8.0. Such bases include ammonium hydroxide, methanolic ammonia, primary amines such as methylamine, ethylamine, propylamine, butylamine, second amines such as piperidine, dimethylamine, diethylamine, dipropylamine, dibutylamine, methylethylamine, quarternary amines such as tetra-nbutyl ammonium hydroxide, tetramethyl ammonium hydroxide and the like. The hydrolysis reaction is a continuous reaction usually requiring about 1 to 5 minutes, preferably 1 to 2 minutes.

The fiber while passing from the hydrolysis bath to the dryer rollers is held at constant length or subjected to a stretch of from about 1.05 to 3.0 times depending upon the amount of stretch already applied.

After hydrolysis and post-hydrolysis stretch the fiber is passed over a heated godet at a temperature of from about 80 C. to 110 C. which substantially dried the fiber.

In order to obtain fiber of high tenacity an additional heat stretch step is used after the fiber has been dried. This involves drawing the fiber over a heated apparatus such as a hot pin or shoe at a temperature of from about 95 C. to 200 C. while subjecting the fiber to a stretch of from about 1.1 to 5.0 times, preferably about 1.1 to 2.5 times. In general the higher the amount of hot draw, the higher the tenacity.

To further understand the invention reference will be made to the attached drawing that forms part of the present application.

The drawing is a side elevational view partly in section showing schematically an apparatus arrangement of a type which can be used in carrying out the process of the present invention.

Referring now to the drawing, a water coagulable solution comprising a polyvinyl ester of a halogenated acetic acid dissolved in an organic oxygen containing liquid is passed under pressure from a supply tank (not shown) through a conduit and thence through a filter pump wherein undissolved particles and foreign materials in the solution are removed. The solution then passes to a spinnerette suitably disposed below the upper surface of coagulating liquid composed primarily of water and contained in an open top spinning trough or bath. The solution may be extruded through a single orifice or a plurality of orifices in the spinnerette to form a filament or bundle of filaments. The extruded streams of polymer are directed through the liquid for a predetermined and sufiicient distance to cause the solution to coagulate as desired. A guide may be employed to define the path taken by the filaments in the bath. Fresh liquid is continuously supplied to the bath through the pipes placed near the bottom of each end of the bath.

The coagulated filaments are withdrawn by the implementation of a positively driven take up roller or other thread advancing means, the peripheral speed of which preferably is synchronized with the extrusion speed so that the filaments during their travel between the spinnerette and the rollers may be attenuated and if desired attenuated up to the point just short of where filamentary breakage occurs. After passing around the take up roller the filaments are directed into a second spinning trough or bath containing boiling water. The filaments are then directed around hydrolysis rollers which are partially submerged in the hydrolysis bath. After hydrolysis the fibers are passed over drier rollers. At this point the 'fil-aments may be taken up on a winder and later hot drawn if desired or directed onto the first hot draw roller, then over a hot pin, then over second hot draw roller. Finally, the fibers are taken up on a cone winder.

The relationship of drawing variables to the ultimate fiber tenacities obtained by the spinning process just described is noteworthy because a number of widely varying drawing combinations may be used to obtain fibers having tenacities better than 9 grams per denier. Typical variations are found in Table I.

1 Does not include jetstretch.

Two specific requirements have been determined. First the hot draw step is necessary for high tenacity and the jet stretch, the stretch imparted to the fiber between the spinnerette face and the take up roller, has to be kept very low. For high tenacity fibers, i.e. fibers having tenacities of 9 grams per denier or above, a total stretch (exclusive of jet stretch) of about 7 to 11 times is generally required. Little difference is noted whether the fiber is highly stretched, up to 5 times, or only slightly stretched, about 1.2 times, before it is hydrolyzed. Characteristic tensile properties of the high strength and low strength stereoregular polyvinyl alcohol fibers of this invention are shown in Table II.

The highest average tenacity obtained was 13.7 grams per denier. Tenacities of 9 to 11 grams per denier are obtained without undue difiiculties. Polymers from different polymerizations give equally good fibers; samples 1 through 4 of Table I all were from different polymerization runs.

characteristically, and as would be expected, low elongation often accompanied high tenacity. The ease, however, with which it is possible to obtain elongation below 7 percent was surprising. Elongations as low as 4 percent were Obtained.

Another surprising feature of this invention is the great loss in fiber weight which is so easily tolerated by the fiber, and yet results in a fiber having very excellent tensile properties. In the conversion of polyvinyl trifluoroacetate topolyvinyl alcohol, the theoretical weight loss is 69 percent. Thus, over two-thirds of the original weight of the spun fiber is lost in the hydrolysis step.

The effect of polymer molecular weight on the spinning process and the properties of the resultant fibers is not noticeable within the range of usual spinning viscosities. No noticeable dilferences were observed in the spinnability of polymers having intrinsic viscosities within the range of 0.57 to 0.9, nor were significant differences observed in ultimate fiber properties obtained.

In the case of polymers of lower molecular weight ranges, solutions containing up to about 38 percent by weight of polymer may be spun whereas in the case of higher molecular weight polymer the concentration of polymer in the spinning solution was necessarily lower. This factor strongly favors the use of lower molecular weight polymer to produce fibers having the ultimate in desirable properties.

The fibers of this invention exhibit good hot wet properties. High strength fibers that have been relaxed in boiling water actually show about the same tenacity in water at 70 F. or when measured at standard conditions. In some cases they were actually stronger in Water at 70 F. Even in the case of quite low tenacity fiber, the differences in the elongations and tenacities of fiber in water of 70 F. and those measured at standard conditions for boiled off fiber were small. In water at 200 F. high tenacity fibers usually retained about 60 percent of their original tenacity and about 70 percent of their boiled olf tenacity with elongations usually ranging from 10 to 20 percent. The boiling water shrinkage of these fibers varied greatly with the tenacity of the fiber. It reached a minimum value of around percent for high tenacity fibers. The moisture regain also increased with decreasing tenacity, the values ranged from about 5 percent to 9 percent at'65 percent R.H.

In general, the fibers of this invention may be characterized as having very high strength, up to 14 grams per denier tenacity, with tenacities in the range of 9 to 13 grams per denier tenacity :being readily obtained. Very low elongations at high strength are possible but, on the other hand, the fibers can be prepared with normal tenacity and elongation. They have good hot wet properties, light stability is better than nylon 66. Good growth properties, high fiber modulus, good heat stability, and excellent knot strength are other characteristic features of the fibers of this invention.

The fibers of this invention are useful in a Wide variety of commercial center or industrial and other uses. In the form of fibers and filaments, they may be used as filters,

industrial belting, reinforcement in laminates and plastics, apparel and tire cord.

The invention is further illustrated by the following examples in which all parts and percentages are by weight unless otherwise indicated.

Example I A 15 gram portion of stereoregular polyvinyl trifluoroacetate was dissolved in grams of acetone which had been dried over anhydrous sodium sulfate to give a clear, colorless, viscous solution containing 15 percent solids. The polyvinyl trifluoroacetate had an intrinsic viscosity of 2.75 as measured in methyl ethyl ketone at 25 C.

For the spinning of this solution a conventional wet spinning machine was used. The solution was wet spun through a 10 hole spinnerette into a bath of water at room temperature. The coagulated fiber was run over 1 set of godets, then to a second set on which the fiber was wrapped 20 times. The fiber on this set of godets was allowed to remain for approximately 2 minutes while the godets rotated in a pan of ammonium hydroxide (2.8 percent NH The fiber was hydrol-ized continuously to stereoregular polyvinyl alcohol fiber during the 2 minute period. Then the fiber was passed over a set of steam heated drying rolls and on to a take up spool. A portion of the fiber was machine drawn across a hot pin at 190 C. with an almost maximum stretch which resulted in an increase in length of approximately 60 percent. Infrared examination of the fiber showed that it was essentially completely hydrolized. Single filament testing of the fiber was conducted and the results are shown below in tabular form.

Boiling Water Shrinkage=5.3%.

Example III To a 206 gram portion of stereoregular polyvinyl trifluoroacetate there was added 352 grams of dry acetone. The ingredients were mixed thoroughly, heated to 32 C., and agitated for 2 hours to produce a clear solution with a viscosity of about 1200 centipoises. The solution was extruded at a temperature of 23 C. through a conventional spinnerette into a water coagulation bath, the fibers were continuously withdrawn from the bath using a jet stretch of 0.24, and then were stretched 2.3 times their length in a boiling water bath. Continuous hydrolysis was accomplished using two godets and ammonium hydroxide as in Example II. After hydrolysis the resulting polyvinyl alcohol filaments were stretched 2.7 times while wet, dried on rollers heated to 80 C., then drawn 2.1 times over a heated draw pin at C. The filaments had a denier of 1.3, an average tenacity of 13.7 grams per denier, with individual breaks over 15 g.p.d., and an elongation of 6 percent.

Example IV A series of spinnings were conducted to determine the versatility of the hot stretch step of the spinning process for high and low tenacity fibers. All samples were spun according to Example I and the results are tabulated below.

This data shows that the hot stretch is necessary in order to obtain high tenacity fibers.

The foregoing detailed description has been given for clearness of understanding only, and unnecessary limitations are not to be construed therefrom. The invention is not to be limited to the exact details shown and described since obvious modifications will occur to those skilled in the art, and any departure from the description herein that conforms to the present invention is intended to be included within the scope of the claims.

I claim:

1. In a process for the preparation of boiling water insoluble stereoregular polyvinyl fibers, the improvement consisting in extrusion of a solution of a polyvinyl ester of a haloacetic acid and continuously hydrolyzing the resulting shaped article.

2. A process for the preparation of boiling water insoluble stereoregular polyvinyl alcohol fibers comprising the steps of (1) extruding a solution of a stereoregular polyvinyl ester of a halogenated acetic acid into a coagulation medium,

(2) stretching the resulting fiber,

(3) hydrolyzing the fiber continuously,

(4) drying the fiber,

(5) and hot drawing the fiber.

3. A process for the preparation of boiling Water insoluble stereoregular polyvinyl alcohol fibers comprising the steps of (1) extruding a solution of from 12 to 40 percent by weight of a stereoregular polyvinyl ester of a halogenated acetic acid dissolved in an organic oxygen containing liquid into a coagulation bath containing a liquid which is a non-solvent for the polymer,

(2) stretching the resulting fiber,

(3) hydrolyzing the fiber continuously,

(4) stretching the fiber immediately after hydrolysis,

(5) drying the fiber by passing said fiber over a heated surface, and

(6) hot drawing the fiber.

4. The process of claim 3 wherein the organic oxygen containing liquid is acetone.

5. The process of claim 3 wherein the organic oxygen containing liquid is methylethyl ketone.

6. The process of claim 3 wherein the organic oxygen containing liquid is tetrahydrofuran.

7. The process of claim 3 wherein the organic oxygen containing liquid is dimethylacetamide.

8. The process of claim 3 wherein the hydrolysis agent is ammonium hydroxide.

9. The process of claim 3 wherein the hydrolysis agent is methanolic ammonia.

10. The process of claim 3 wherein the hydrolysis agent is tetramethyl ammonium hydroxide.

11. The process of claim 3 wherein the hydrolysis agent is a primary amine.

12. The process of claim 3 wherein the hydrolysis agent is a secondary amine.

13. stereoregular polyvinyl alcohol fibers produced according to the process of claim 3 having a tenacity greater than 8 g.p.d.

14. A process for the preparation of boiling water insoluble stereoregular polyvinyl alcohol fibers comprising the steps of (1) extruding a solution of a stereoregular polyvinyl ester of a halogenated acetic acid dissolved in an organic oxygen containing liquid into a coagulation bath containing a liquid which is non-solvent for the polymer,

(2) stretching the resulting fiber from 1.05 to 8.0 times in a hot aqueous bath,

(3) hydrolyzing the fiber continuously with a hydrolysis agent which is a base having a pKb value less than 8.0,

(4) stretching the fiber immediately after hydrolysis,

(5) drying the fiber by passing said fiber over a heated roller at a temperature of from C. to C.

(6) and drawing the fiber over a heated surface while subjecting said fiber to a stretch of from 1.1 to 5.0 times.

15. A process for the preparation of boiling water insoluble stereoregular polyvinyl alcohol fibers comprising the steps of (1) extruding a solution of from 12 to 40 percent by weight of vinyl trifiuoroacetate dissolved in acetone into a coagulation bath comprising water,

(2) stretching the resulting fiber from 1.05 to 8.0 times in a boiling water bath,

(3) hydrolyzing the fiber continuously with ammonium hydroxide for a period of time of from 1 to 3 minutes,

(4) stretching the fiber immediately after hydrolysis,

(5) drying the fiber by passing said fiber over a heated roller at a temperature of from 80 C. to 110 C.

(6) and drawing the fiber over a heated surface while subjecting said fiber to a stretch of from 1.1 to 5.0 times.

16. A process for the preparation of boiling water insoluble stereoregular polyvinyl alcohol fibers comprising the steps of (l) extruding a solution of from 12 to 40 percent by weight of vinyl chlorodifiuoroacetate dissolved in acetone into a coagulation bath comprising water,

(2) stretching the resulting fiber from 1.05 to 8.0

times in a boiling water bath,

(3) hydrolyzing the fiber continuously with ammonium hydroxide for a period of time of from 1 to 3 minutes,

(4) stretching the fiber immediately after hydrolysis,

(5) drying the fiber by passing said fiber over a heated roller at a temperature of from 80 C. to 110 C.

(6) and drawing the fiber over a heated surface while subjecting said fiber to a stretch of from 1.1 to 5.0

times.

References Cited UNITED STATES PATENTS 2,936,488 5/1960 Cotlet et al. 26091.3 X

FOREIGN PATENTS 482,216 3/1938 Great Britain.

ALEXANDER H. BRODMERKEL, Pliffldl') Examiner.

I. H. WOO, Assistant Examiner. 

1. IN A PROCESS FOR THE PREPARATION OF BOILING WATER INSOLUBLE STEREOREGULAR POLYVINYL FIBERS, THE IMPROVEMENT CONSISTING IN EXTRUSION OF A SOLUTION OF A POLYVINYL ESTER OF A HALOACETIC ACID AND CONTINUOUSLY HYDROLYZING THE RESULTING SHAPED ARTICLE. 